Question

Find the value of the following :

(i) sin 70° sin 20° – cos 20° cos 70°

(ii) 2cos67°/sin23° - tan40°/cot50° – cos 60°

Answer 1

(i) sin 70° sin 20° – cos 20° cos 70°

= sin(90° – 20°)sin 20° – cos 20° cos(90° – 20°)

= cos 20° sin 20° – cos 20° sin 20°

= 0

(ii) 2cos67°/sin23° - tan40°/cot50° – cos 60°

= 2 – 3/2

= 1/2